Put to bottom of layer by default!
Also i think it would be very cool if you could have an icon to quickly toggle weather objects are placed on the top or on the bottom of the z-order of all the objects on the active layer....

As i often find my self digitizing from the bottom...this actually makes things a little easier in some respects as managing overlap is allot easier when you are creating objects that are underneath existing ones instead of perhaps creating objects that will latter have subsequent overlaid objects ETC which can get complex ETC and result in incorrect overlap in some instances...

Anyway digitizing from the bottom is handy and could be easily catered to i think.

Not the most critical feature, but I see how that can be useful, depending on your style. A toggle button would definitely be a great for this.

draw, hit the end key. Not particularly complicated.